Self-consciousness is the knowledge of one's own presence. There are many categories of consciousness, but self-consciousness is the specific ability of meta-consciousness – the awareness of one's awareness. Self-consciousness is not the idea that "I exist", it is the idea that "others know I exist".
Jean Paul Sartre describes self-consciousness as being "non-positional", in that it is not from anywhere in particular.
It is a unique type of consciousness in that it not always present, and it is not sought after. Unlike self-awareness, self-consciousness has connotations of being unpleasant, and is often linked to self-esteem. Self-consciousness is credited with the development of identity, because it is during periods of self-consciousness that people come the closest to knowing themselves objectively. Self-consciousness plays a large role in behaviour, as it is common to act differently when people "lose themselves in a crowd". Self-consciousness affects people in varying degrees, as some people are in constant self-monitoring, while others are completely oblivious about the reality of their existing self. Different cultures vary in the importance they place on self-consciousness.

The ability to self-analyze (or scrutinze) is widely believed among psychologists not to develop until mid-childhood, and arguably is present in only a few species of animals. Tests performed for self-consciousness include applying a bright dot to a subjects forehead, and then placing them in front of a mirror – if they reach for their own forehead, it appears they are self-conscious. It is widely believed that self-consciousness is most present during the teenage years.

It is often felt that self-consciousness impairs one's ability to perform complex actions. For example, piano players sometimes cannot play difficult passages when they realise they are playing them.

Self-consciousness also refers to shyness or introvertism sometimes. For example, the term may be applied to cases in which one is "self-conscious" of a negative trait, usually physical, like acne or obesity, and afraid of the judgments of others. Thus, self-consciousness can be a motivator for social isolation.